Pressure loaded pump



Dec. 8, 1959 F. E. NORLIN 2,915,981

PRESSURE LOADED PUMP Filed Oct. 5, 1953 [raver-liar: Francis i Nor-[71,

United States Patent PRESSURE LOADED PUMP Francis E. N'orlin, Chesterland, Ohio, assignor to Borg- Warner Corporation, Chicago, 111., a corporation of Illinois Application October 5, 1953, Serial No. 384,265

4 Claims. (Cl. 103-126) This invention relates to a gear pump and more par ticularly to a gear pump of the type employing pressure loaded bushings, such pumps sometimes being referred to as pressure loaded pumps.

In a pressure loaded pump of the type including one set of axially movable, pressure loadable bushings, a part of the discharge pressure generated by the .pump is communicated to the rear or motive pressure surface of the axially movable bushings to urge the bushings into sealing relationship with their associated gears. As described in the United States Patent No. 2,420,622 to Lauck et al., by carefully selecting the relative areas of the forward surfaces and the rear or motive surface of the bushings, it is possible to control within very close limits the actual sealing pressure established during operation of the pump. Gear pumps so constructed are capable of delivering fluid at extremely high pressure with considerable volume.

Because the pressure loadable bushings must be able to move axially, a certain initial minimum clearance must be provided between the sides of the bushings and the adjacent sides of the chambers or bores in the pump housing cover in which the bushings are received. In practice, this clearance is actually very slight, but it has been found that, due to the rotational movement of the gears during pumping operation, each of the bushings tend to twist or rotationally follow its associated gear because of frictional torque between the gears and the bushings; which twisting not only tends to change the center distance of the bushings, i.e., a change in the distance the bushing twists from its original position as assembled and/or a position at the time the pump is not in operation, but also tends to provide leakage paths for fluid under pressure, not only between the bushings themselves but between the bushings and housing. Thus, not only the pressure generated by the pump and communicated to the rear or motive surfaces of the bushings, but also that pressure generated by the pump in the pumping chamber itself will find a leakage path and return to inlet. Accordingly, it is evident that this twisting or skewing, as it is sometimes called, of the bushings can cause a reduction in the overall efficiency of these pumps because of the leakage paths formed.

Accordingly, one solution to the problem of preventing leakage in a pressure loaded pump, of the type herein described and constructed in accordance with the aforementioned Lauck et a1. patent, is to provide a means for preventing twisting or skewing of the bushings during operation of the pump. This is accomplished by providing the bushings, atthe juncture thereof, with a recess for receiving a reacting member in the form of a locating means which will react against the forces caused by the tendency of the bushings to twist or skew.

Accordingly, one object of the present invention is to provide a means whereby the tendency of the bushings to twist or skew during operation of the pump can be substantially reduced.

A further object of the present invention is to provide "ice a means whereby the tendency of bushing twisting or skewing can be substantially reduced by providing a recess in the flanged portion of the bushings and located at the juncture of these bushings to receive a locating resilient member, the latte-r forming a reaction member to the normal torque caused by the frictional torque between the bushings and the gears.

Another object of the present invention is to provide a means whereby the tendency of bushing twisting or skewing can be substantially reduced by providing a recess in the flanged portion of the bushings and located at the juncture of these bushings to receive a locating spring member which will define a reaction member to the normal torque caused by the frictional torque between the bushings and the gears.

A further object of the present invention is to provide a means whereby the tendency of bushing twisting or skewing can be substantially reduced by providing a recess in the flanged portion of the bushings and located at the juncture of these bushings to receive a locating dowel pin member, the latter forming a reaction member to the normal torque caused by the frictional torque between the bushings and the gears.

A still further object of the present invention is to provide a means for substantially increasing the volumetric efiiciency of the pressure loaded pump of the type described by preventing twisting or skewing of the bushings during operation.

In accordance with one embodiment of this invention, the rear or motive pressure responsive surface of each of a set or pair of pressure loadable bushings is provided with complementary recesses at the point of juncture, which complementary recesses define or form a larger unitary elongated recess when the bushings are in assembled relationship, in which recess is received a resilient reacting member which may take the form of a locating spring. This reacting member is so arranged that the twisting or skewing of one of the pair of bushings, which tends to move a portion of one side of the unitary elongated recess and cause a sliding action at the juncture of the bushings, is resisted by oppositely directed forces of the reacting member. This substantially reduces the tendency of the bushings to form leakage paths between the housing cover and bushings, or between the bushings themselves, and substantially increases the overall efficiency of the pump. In this embodiment, these complementary recesses, wherein the reacting member is located, are formed with sufficient depth to allow the axially movable bushings to independently move or change their position, such as, for example, due to any pressure unloading accomplished by movement of the bushings, or due to any wear on the side face of the bushings, without substantially reducing the efficiency of the reacting member and causing any misalignment or mislocation thereof. It has been found in practice that by properly determining the size and depth of these recesses and by properly determining the strength or resiliency of the locating member, that that the twisting or skewing of the bushings can be substantially reduced and proper positioning of the bushings is provided during operation of the pump.

In accordance with the second embodiment of this invention, each of a pair of bushings is provided with complementary recesses in which are received a reacting member in the form of a dowel pin member. These recesses are so located to provide at the juncture of the bushings a unitary elongated recess and a means of preventing twisting or skewing by allowing a portion of the opposite ends of the complementary recesses to act against an end of the pin member in such a manner that the twisting and sliding action is restricted by the pin member. By proper selection of the size and location of the recesses 'and the length of the dowel pin member any twisting or skewing can be substantially reduced.

Other objects, features and advantages of the present invention will be apparent from the following detailed description, taken in conjunction with the drawings; wherein:-

v Fig. l is a fragmentary, axial, sectional view of a pressure loaded type intermeshing gear pump constructed in accordance with one embodiment of the invention;

Fig. 2 is a cross sectional view taken substantially along line 22 of Fig. 1, showing to advantage the bushingconstruction. employing the first embodiment of this invention;

Fig. 3 is an enlarged, fragmentary, axial, sectional view showing to advantage the location and depth of the recess and spring member of thefirst embodiment of this invention;

Fig. 4*is an enlarged, fragmentary, axial, sectional, semi-schematic view of the recess showing the tendency of the recess to offset during operation of the pump; and

' V Fig. 5 is an enlarged, fragmentary, sectional view showing the bushings. in section, similar to Fig. 2, but showing to advantage the second embodiment of this invention.

Referring now to the drawings, numeral denotes a suitably chambered pump housing in which are rotatably mounted a driven gear 11 and an intermeshing driving gear 12. Driven gear 11 is supported on a shaft 13 journaled on its right end through a flanged, pressure responsive, axially movable bushing 14 and on its left side through a fixed, flanged, body bushing 15. The gear 11 and associated bushings 14 and 15 are arranged in a first chamber 16 formed in the pump housing 10' with sufficient clearance between the right end of bushing 14 and the adjacent wall of the housing to permit axial movement of the bushing 14. Similarly, driving gear 12 has disposed on its right side a flanged, pressure responsive, axially movable bushing 17 and on its left a fixed, flanged, body bushing 18. Driving shaft 19', upon which gear 12 is mounted, is journaled through bushings 17 and 18 and may be suitably connected to any driving means (not shown). Gear 12 and associated bushings 17 and 18 are located in a second chamber 20 formed in the housing adjacent and parallel to chamber 16. Sufficient clearance is provided between the right end of the bushing 17 and the adjacent end wall of the housing to permit axial movement of the bushing 17.

As shown in Fig. 2 of the drawings the housing has an inlet port or conduit 21 formed on its left side and an outlet port or conduit 22 formed on its right side. Low pressure fluid is introduced in the pump housing at the inlet 21 and high pressure fluid is discharged from the housing through outlet'22, the inlet and outlet ports communicating with the inlet and discharge areas of the pump gears. The pressure loadable bushings are normally fitted into the bores with sufficient clearance to permit slight axial movement of the bushings with respect to the bores to establish the desired pressure loaded seal during operation of the pump.

In the operation of the pump of this type, discharge pressure generated by the intermeshing gears is communicated from the outlet or discharge side thereof to the annular pressure loaded areas at the back of the bushing, designated at 23 and 24 in the drawings, through an axially extending passage 25 formed in the peripheries of the flanged portions of the bushings on the discharge side of the pump at the point of convergence of the flanged portions of the bushings. Areas 23 and 24 cooperate withthe adjacent walls of the housing bores 16 and 20, respectively, and the periphery of the barrel portion of the bushing define annular pressure loading chambers 26 and 27, respectively, the passage '25 extends from the discharge side ofthe gears to the right as viewed in Fig. 1 to the inner communicating portions of the pressure loading chambers 26 and 27 at their point of juncture.

Escape of pressure rearwardly from the pressure loading chambers is substantially prevented by means of an O- ring seal 28 disposed about the periphery of the rear or barrel portion of each bushing in a suitable annular Pressure leaking past the O-ring seal may be vented to inlet pressure or to a zone of intermediate pressure in line .with conventional pressure loaded pump practice as set forth in the above referred to Lauck et-al. patent.

To provide an initial sealing relationship between the bushings and the gear side faces, coiled compression springs 29 and 30 are disposed within the right ends of the chambers 16 and 20, respectively, so as toseat against the terminal ends of the parallel barrel or tubular portions to urge the forward surface of these bushings into engagement with the gear side faces.

In the usual pressure loaded pump constructed in accordance with the teaching of the aforementioned Lauck et al. Patent No. 2,420,622, relief recesses 31 and 32 are formed in the radially inner portions of the forward or gear engaging surfaces of the pressure loading bushings 14 and 17, or in the gear side faces, and are placed in communication with a pressure lower than discharge pressure generated by the pump through the usual clearance between the gear journals and the bushing bores or by specific grooves or channels extending axially of the inner cylindrical surface of the tubular part or bore of the forces communicated to the rear surfaces of the bushings,

which latter axial forces are made to slightly exceed the first mentioned axial forces and thereby maintain proper sealing engagement.

As hereinabove mentioned, since it is necessary to fit the bushing with some clearance in the bushings receiving chamber to permit slight axial movement required of the bushings in order to establish the proper seal, it has been found in practice that there is a tendency of the bushings to slightly twist or skew within the housing as a result of frictional torque between the gear side face and shaft and the bushings forward face and journal. This twisting or skewing may shift the bushings and cause a sliding action at the juncture therebetween to sufliciently establish a clearance between the bushings and the housing, which clearance is maintained during the operation of the pump and may provide a communication of discharge pressure from the dischargeside of the gears and from the aforementioned pressure loading chambers 26 and 27 back to the inlet side of the pump, thus substantially reducing the overall efiiciency of the pump.

As hereinbefore mentioned, it is a purpose of the I present invention to reduce the tendency of the bushings v the discharge side towards the inlet side.

to twist as skew with respect to the bearing bores in the housing thereof by providing a means which 'will c0- operate with each of the bushings and restrict throughout the entire operation of the pump their tendency to twist and skew, reducing the tendency of leakage of fluid from This means comprises a reacting member received in a recess and located at the juncture of the bushings in such a manner that each bushing cooperates in an'opposite direction due to the sliding action at the juncture of the bushings with the opposite sides of the reacting member to thus present additive forces which are restricted by the reaction of the reacting member.

More particularly, in the embodiment shown in Figs. 1,

2 and 3, the rear portions of the axially movable bushings are provided with complementary recesses 33 and 34, respectively, which when in assembled relationship, form a substantially rectangular elongated recess designated in its entirety by 35 and having its major axis located in a horizontal position and perpendicular to the axis of rotation of the gears substantially midway of the juncture of the bushings. A resilient member, shown in the drawings as helical locating spring 36, is positioned in the recess 35 under compression so that the opposite ends thereof react against the ends of each of the complementary recesses 33 and 34 to maintain the latter in substantial alignment so that a rectangular configuration as shown in Fig. 2 is maintained.

In the usual operation of pressure loaded pumps of the type described herein, in order that inlet pressure may be introduced into an inlet port 21 and discharged at the high pressure from annular port 22, the driving gear 12 may be rotated in a clockwise direction and its complementary intermeshing driven gear 11 is then rotated in a counterclockwise direction. It is evident that, from the clockwise movement of the driving gear, its associated axially movable bushings 17 will tend to follow or twist with respect to the housing and bore 20 due to the frictional torque provided by the driving gear 12 and bushings 17. Similarly, the frictional torque provided by the driven gear 11 as it rotates in a counterclockwise direction, will tend to cause its associated bushing 15 to rotate counterclockwise. In practice it has been found that frictional torque will not be evenly distributed between the axially movable bushings because one bushing may be subject to more friction than the other, which will cause that bushing to tend to twist more. As a consequence of this uneven torque, one bushing will follow the other bushing in its twisting movement causing a sliding action between the bushings at their juncture with a resultant offsetting of the sides of the rectangular elongated recess as shown in exaggerated proportions in Fig. 4. Since these bushings 14 and 17 are provided with slight minimum clearance due to the necessity of limited axial movement thereof, it is apparent that leakage paths will be provided between the bushings and the discharge side of the pump, thus reducing the overall efliciency of the pump. Obviously, the rectangular arrangement of the recess 35, which is formed by the two complementary recesses 33 and 34, when in assembled relationship will tend to become offset because of the tendency of the bushings to twist and because of the sliding action at the juncture of the bushings, one end of the recess 33 will act in a direction to the left as viewed in Fig. 2 and one end of complementary recess 34 will act in a direction towards the right as viewed in Fig. 2. The reacting member, in this instance the helical spring 36, will oppose the forces created by the movement of the right and left ends of the complementary recesses and will urge these offset ends towards their original positions, which in turn tend to reduce the twisting movement of the bushings. It is to be noted that forces created by the right end portion of the complementary recess 33 acting towards the left and the left end portion of the recess 34 acting towards the right are additive forces and the spring 36 complements these two forces by its compression and then the tendency to twist is substantially reduced.

In pressure loaded pumps of the type described herein, there may be a tendency of one forward surface of the bushing to wear at a different rate than the other forward surface of the bushing, or during operation of the pump one axially movable bushing may move away from its associated gear side face independently of the other due to the unloading ability of these axially movable bushings. Accordingly, in order to prevent the reacting member from becoming displaced from its recess 35, the recesses 33 and 34 are cut deep enough into the back portion of the bushing, as clearly shown in Fig. 3, to

6 provide for any movement of either one of the bushings without displacement of the loading spring 36.

In the embodiment shown in Fig. 5 the same reference numerals are provided as used in connection with the embodiment shown in Figs. 1, 2, 3 and 4, with the exception of reference numeral 36. In this embodiment the elongated, rectangular, horizontal recess 35, comprising the complementary recesses 33 and 34 and having its major axis located horizontally and at right angles to the axis of rotation of the pumping gears, receives a reacting member in the form of a dowel pin member 37. Ohvious-ly, as in the case of the other embodiment, the tendency of the complementary recesses to become offset to one another, due to the rotation of the gears, the uneven distribution of the rotational friction, and the sliding action of the bushings, is restricted and opposed by the dowel pin member.

Wherein the above features of this invention, relating to the reduction in the tendency of the bushings to twist or skew during operation of the pump, have been drawn to the axially movable, pressure loadable bushings, it will be appreciated that the fixed or body bushings in a pressure loaded pump of this type may likewise have a tendency towards twisting due to the frictional torque between the gears and the bushings. Therefore, in a manner similar to the pressure loaded bushings, the fixed or body bushings may be provided with a means of preventing twisting or skewing in a manner similar to the embodiment illustrated in Figs. 1 to 5, inclusive.

Similarly, the recesses of the embodiment shown in Fig. 5 are cut, in a manner similar to that shown in Fig. 3, to a depth sufficient to prevent any displacement, mislooation or misalignment due to uneven wear of the bushings or due to the pressure unloading capabilities of the bushings. I

As is obvious from the drawings, the bushings of both modifications are formed with complementary flat chordal meeting surfaces which form the juncture of the bushings referred to previously.

Where herein the various parts of this invention have been referred to as located in the right or left position or in clockwise or counterclockwise rotation, it will be understood that this is done solely for the purpose of facilitating description and that such references relate only to the relative position of the parts as shown in the accompanying drawings.

While this invention has been described in its exemplary forms or embodiments, it will be understood to persons skilled in the art, after understanding the improvements, that various changes and modifications may be made therein Without departing from the spirit or scope thereof.

I claim:

1. In a pressure generating pump of the type including a housing containing intermeshing gears and having an inlet leading to and an outlet leading from said housing, axially movable bushings and fixed bushings, each of said bushings having a forward surface engageable with the side face of said gears and formed with a complementary fiat chordal meeting surface, said axially movable bushings being subject to discharge pressure to maintain sealing engagement with the gear side faces during operation of the pump, and means for reducing the tendency of said bushings to follow the rotational movement of the gears and for tending to maintain each bushing in a predetermined rotational position relative to its associated gear comprising complementary recesses formed at the complementary chordal meeting surface of said bushings, a loading spring received in these complementary recesses to react against the side portions of these recesses in a direction opposite to the direction of bushing rotational tendency.

2. In a loading pressure generating pump of the type including a housing containing intermeshing gears and having an inlet leading to and an outlet leading from said housing, axially movable bushings and fixed bushings, each of said bushings having a forward surface engageable with the side faces of said gears and having 'a complementary flat chordal meeting surface, said bushings forming a juncture at said meeting surfaces, said axially movable bushings being subject to discharge pressure to maintain sealing engagement with the gear side faces duringoperation of the pump, and means disposed intermediate the ends of said juncture for reducing the tendency of the bushings to follow the rotational movement of the gears comprising complementary recesses formed in each of said bushings, each of said recesses opening towards the juncture of said bushings and forming a unitary elongated recess having its major axis parallel to said juncture, a loading spring received in said unitary recess to react against the side portions of said complementary recesses in a direction opposite, to the direction of bushing rotational tendency.

3. In a'loading pressure generating pump of'the type including a housing containing intermeshing gears and having an inlet leading to and an outlet leading from said housing, axially movable bushings and fixed bushings, each of said bushings having a forward surface engageable with the sidefaces of said gears and having a complementary flat chordal meeting surface, said bushings forming a juncture at said meeting surfaces, said axially movable bushings being subject to discharge pressure to maintain sealing engagement with the gear side faces during operation of the pump, and means disposed intermediate the ends of said juncture for reducing the tendency of the bushings to follow the rotational movement of'the gears comprising complementary recesses.

formed in each of said bushings, each of said recesses opening towards the juncture of said bushings and forming a unitary elongated recess having its major axis parallel to said juncture and perpendicular to the axis of rotation of said'gears, a loading spring received in said unitary recess to react against the side portions of said complementary recesses in a direction opposite to the direction of bushing rotational tendency.

' 4. A pressure loaded type intermeshing gear pump including a housing having a pair of pumping chambers. formed therein and having an inlet leading to and an out let leading from said pumping chambers, intermeshing.

pumping gears disposed in said chambers and arranged to force liquid from said inlet through said chambers and out said outlet, bushings operatively associated with each of said pumping gears and having complementary.

fiat chordal meeting surfaces,said bushings being axially movable in response to application of discharge pressure to the rear surface thereof to engage the operatively associated gear side faces in sealing relation, means disposed intermediate the ends of said meeting surfaces for reducing the tendency of said axially movable bushings to follow the rotational movement of their opera-.

References Cited in the file of this patent UNITED STATES PATENTS 621,280 v Pitt Mar. 14, 1899 2,420,622 'Roth et a1. f May 13, 1947 2,487,732 Schanzlin Nov. 8, 1949 2,627,232 Lauck Feb. 3, 1953 2,649,740 Murray et al. Aug. 25, 1953 2,660,958 Lauck Dec. 1, 1953 2,706,452 Hilton Apr. 19, 1955 2,756,681 Oliver July 31, 1956 FOREIGN PATENTS Australia Aug. 3, 1953 

